1. Field of the Invention
This invention relates to a small swivel type working vehicle, particularly a small backhoe, comprising a running device, a swivel base mounted on the running device to be swivelable about a vertical swivel axis, a driver's seat mounted on the swivel base, a control box mounted upright on a top surface of the swivel base forwardly of the driver's seat, a swing bracket supported to be swingable about a vertical pivotal axis by a flange unit provided at a front end of the swivel base, a boom attached to the swing bracket to be swingable about a horizontal shaft, and a boom cylinder connected at one end thereof to the swing bracket and at the other end to the boom for swinging the boom.
2. Description of the Related Art
A small backhoe of the type described above is known from Japanese Patent Publication Kokai No. 8-134948, for example.
It is easy for a large or midsize backhoe with a sufficiently large swivel base to secure an accommodation space around the driver's seat and a walk-through space enabling the driver to board and alight from the backhoe at opposite lateral sides. With a small backhoe, however, it is difficult to be capable of normal operations while securing such spaces noted above. Attempts to secure minimum accommodation and walk-through spaces result in disadvantages of a bad fore and aft balance of the swivel base and a reduced swing angle of the boom. Particularly, securing an appropriate walk-through space is closely related to a layout of the control box on the swivel base.
The conventional backhoe generally includes numerous control valves for controlling supply of pressure oil to actuators such as right and left propelling motors, a swivel motor, a dozer cylinder, a boom cylinder, an arm cylinder, a bucket cylinder, a swing cylinder and the like, and a control device for controlling the control valves. The control device is mounted in the control box while the control valves are arranged inside the swivel base remote from the control box.
Transmission of operating forces from the control device to the control valves may be made either through links and rods operatively connected to control levers, as in the case of mechanical control valves such as control valves for the right and left propelling motors, for the dozer, for swinging and the like, or by operating pilot valves through control levers to control hydraulic control valves such as those for swiveling, for the boom and arm and the like by pilot pressure.
To control the control valves by pilot pressure requires frequent and delicate operations, and the numerous valves mounted within the control box are controlled by a pair of right and left control levers.
The control box accommodates only the control device and the control valves are mounted within the swivel base remote from the control box. Thus, the control box per se is not required to have such a large fore and aft dimension, and may allow a large distance between the rear surface of the control box and the driver's seat to secure space around the driver's feet. However, the control valves are mounted within the swivel base remote from the control box, which hampers a compact arrangement as a whole. Further, since a piping space is required, simplification of the structure becomes difficult. In addition, when the control valves are provided within the swivel base, a space for accommodating the control valves limits a space for accommodating the oil tank, fuel tank or the like within the swivel base.
As one solution, it is conceivable to arrange the control valves below the control device in the control box. However, an arrangement of the control valves within the control box results in an increased fore and aft dimension of the control box. An ultra-small swivel type backhoe in particular allows on a very small distance from the driver's seat to an excavating assembly. Where the control box disposed therebetween has a large fore and aft dimension, the walk-through space is reduced to impair mobility of the driver. Further, the control device could hamper assembly and maintenance of upper portions of the control valves.